The Gmail Notifier is a application that alerts you when you recive a new Gmail message

The Gmail Notifier is a downloadable Windows application that alerts you when you have new Gmail messages.

It displays an icon in your system tray to let you know if you have unread Gmail messages, and shows you their subjects, senders and snippets, all without having to open a web browser.

Once you install the Notifier, you’ll be able to:

Automatically check for new messages every two minutes.

See a snippet of text from up to 30 unread messages.

Select a sound to indicate when you have new mail.

Make Gmail your default email application.

Limitations

Gmail Notifier is made available to you for your non-commercial use only. This means that you may use it at work or at home. But you first need to obtain Google's permission if you want to sell the Gmail Notifier or any information, services, or software associated with or derived from it.

Gdow is a highly configurable Gmail notifier that will check your GMail account for any unread mail and provide a short preview for it
It can notify you with a classic messsage box, a popup balloon (on Windows XP and Vista) or a transparent animated form.

Chrysanth Email Notifier is a POP3, IMAP4 and Gmail notification software that helps you to get notified of every incoming email and even spams in your mail boxes while they are still sitting on the remote email servers.